/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements. See the NOTICE file distributed with this
 * work for additional information regarding copyright ownership. The ASF
 * licenses this file to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations
 * under the License.
 */
package org.apache.hadoop.hbase.io.hfile;

import java.io.DataOutputStream;
import java.io.IOException;

import org.apache.hadoop.hbase.Cell;
import org.apache.yetus.audience.InterfaceAudience;
import org.apache.hadoop.hbase.io.encoding.DataBlockEncoding;
import org.apache.hadoop.hbase.io.encoding.EncodingState;
import org.apache.hadoop.hbase.io.encoding.HFileBlockDecodingContext;
import org.apache.hadoop.hbase.io.encoding.HFileBlockDefaultDecodingContext;
import org.apache.hadoop.hbase.io.encoding.HFileBlockDefaultEncodingContext;
import org.apache.hadoop.hbase.io.encoding.HFileBlockEncodingContext;
import org.apache.hadoop.hbase.io.encoding.NoneEncoder;

/**
 * Does not perform any kind of encoding/decoding.
 */
@InterfaceAudience.Private
public class NoOpDataBlockEncoder implements HFileDataBlockEncoder {

    // TODO_MA 注释：实现
    public static final NoOpDataBlockEncoder INSTANCE = new NoOpDataBlockEncoder();

    private static class NoneEncodingState extends EncodingState {
        NoneEncoder encoder = null;
    }

    /**
     * Cannot be instantiated. Use {@link #INSTANCE} instead.
     */
    private NoOpDataBlockEncoder() {
    }

    @Override
    public int encode(Cell cell, HFileBlockEncodingContext encodingCtx, DataOutputStream out) throws IOException {
        NoneEncodingState state = (NoneEncodingState) encodingCtx.getEncodingState();
        NoneEncoder encoder = state.encoder;

        /********
         * TODO_MA 马中华 https://blog.csdn.net/zhongqi2513
         *   注释：
         */
        return encoder.write(cell);
    }

    @Override
    public boolean useEncodedScanner() {
        return false;
    }

    @Override
    public void saveMetadata(HFile.Writer writer) {
    }

    @Override
    public DataBlockEncoding getDataBlockEncoding() {
        return DataBlockEncoding.NONE;
    }

    @Override
    public DataBlockEncoding getEffectiveEncodingInCache(boolean isCompaction) {
        return DataBlockEncoding.NONE;
    }

    @Override
    public String toString() {
        return getClass().getSimpleName();
    }

    @Override
    public HFileBlockEncodingContext newDataBlockEncodingContext(byte[] dummyHeader, HFileContext meta) {
        return new HFileBlockDefaultEncodingContext(null, dummyHeader, meta);
    }

    @Override
    public HFileBlockDecodingContext newDataBlockDecodingContext(HFileContext meta) {
        return new HFileBlockDefaultDecodingContext(meta);
    }

    @Override
    public void startBlockEncoding(HFileBlockEncodingContext blkEncodingCtx, DataOutputStream out) throws IOException {
        if(blkEncodingCtx.getClass() != HFileBlockDefaultEncodingContext.class) {
            throw new IOException(this.getClass().getName() + " only accepts " + HFileBlockDefaultEncodingContext.class
                    .getName() + " as the " + "encoding context.");
        }

        HFileBlockDefaultEncodingContext encodingCtx = (HFileBlockDefaultEncodingContext) blkEncodingCtx;
        encodingCtx.prepareEncoding(out);

        NoneEncoder encoder = new NoneEncoder(out, encodingCtx);
        NoneEncodingState state = new NoneEncodingState();
        state.encoder = encoder;
        blkEncodingCtx.setEncodingState(state);
    }

    @Override
    public void endBlockEncoding(HFileBlockEncodingContext encodingCtx, DataOutputStream out, byte[] uncompressedBytesWithHeader,
            BlockType blockType) throws IOException {
        encodingCtx.postEncoding(BlockType.DATA);
    }
}
